An exhaust system for an internal combustion engine is provided. The engine comprises an exhaust line, at least one exhaust gas aftertreatment device arranged in the exhaust line, and a heat source and a heat sink arranged in separate branches of the exhaust line upstream of the exhaust gas aftertreatment device, an exhaust gas flow rate through each respective separate exhaust branch controlled by at least one flow control device. In this way, the temperature of the exhaust entering the aftertreatment device may be controlled by an amount of exhaust that flows through each branch of the exhaust line.